So the A/C light just blinks on me. Research tells me there are actually 12 sensors on this hvac system. So I just brought it in so they could put it on a scan tool. Come to find out its low on refrigerant. Crap! so there's a leak somewhere. I've never really dealt with A/C before, so what do you think? The shop said they can recharge the system and put a dye in it so they can find the leak with a black light sometime down the road for $150. Should I have the shop do it , or is there a cheap recharge can at the parts store with a dye additive?

Get ahead of the game by just adding some refrigerant with dye yourself. Any auto parts store will have the proper fitting/hose/can-tap for an easy fill. Once the dye is in, if it leaks out again itíll be easy to spot the problem.

No, i don't have any friends with gauges or a leak detector. what's a leak detector? Like a leak down test?

I assume if I got a bottle at the parts store with the gauge on it, that will tell me if I have any pressure in the system?

Can you recommend a refrigerant with dye off amazon? They'll probably ship it to me faster than i can get to a store

The dye can be seen with a UV light and yellow glasses. If your system is truly empty, adding one can should give it enough life to at least turn on. Itís not REALLY technical to just add a can so long as you have the proper fitting, which again, you can get cheaply. Iíve seen cans at auto parts stores that already have the proper hose & fitting attached. The fittings are all standardized so you can only hook up to the low pressure side. Regarding brands, I think theyíre all the same. 134A is 134A, so buy whatever you can find. Just start the truck, turn on the A/C, hook up the fitting and open the can, then wait. It may take a half hour for the can to empty, but if the can is frosty, youíll know itís discharging. If your system will hold any pressure your compressor should kick on within the first minute of charging.

The thing is you don't want to dump refrigerant into a system that has leaked down to zero and now has air in it. The air needs to be evacuated out first to avoid high head pressure and contaminants.

I never used a parts store bottle with a gauge so I don't know the answer but I would guess the gauge would show pressure in the system before you start opening up the bottle. (I always use gauges and a 30 Lb drum.)

Anyway, dumping refrigerant into the suction side with engine running only takes a few minutes, not an hour.

I use a leak detector a little like this one.

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The thing is you don't want to dump refrigerant into a system that has leaked down to zero and now has air in it. The air needs to be evacuated out first to avoid high head pressure and contaminants.

I never used a parts store bottle with a gauge so I don't know the answer but I would guess the gauge would show pressure in the system before you start opening up the bottle. (I always use gauges and a 30 Lb drum.)

Anyway, dumping refrigerant into the suction side with engine running only takes a few minutes, not an hour.

I use a leak detector a little like this one.

huh, never knew that tool existed. I would just assume, no refrigerant automatically means there's a leak.

Well, there has to be a leak if the system is low but if you can't determine if there is any pressure in the system now, dump a can in, stop the engine and look/listen for leak (sometimes an oily spot).

Probably 90% of the time vehicles still have some refrigerant in them.

Turn the can upside down and dump liquid in until the gauge shows around 35 PSI and the air coming out of the vents is cold.

(I usually open all the doors and put a fan in front of the condenser while adding refrigerant.)

Dean can probably verify this but I have been told never to use the parts store R134 that has sealer in it. Just the raw 134. Not sure if you can buy it with die that does not also have the sealer.

I just did the entire system on my 99 Tahoe. It had been leaking around the compressor body for quite some time. Had been nursing it along with a can every once in a while but it finally gave it up at 250K miles

Mike,
I don't know if that is what I would use. I would go to WalMart or Advance Auto Parts and buy a single can of straight R134, the real stuff, not "equivalent to" If one can doesn't get it running then you might as well have someone find the leak and fix it right.

If you start putting anything other than real 134 in it the guys at the shop are not going to be happy when the time comes to do it correctly.